Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
ROTARY ATOMIZING HEAD
TECHNICAL FIELD
This invention relates to a rotary atomizing head
particularly suitable for use on a coating machine for coating
vehicle bodies or other work pieces.
to BACKGROUND ART
A rotary atomizing head type coating machine which is
advantageous in terms of deposition efficiency and finish
quality is generally resorted to for coating vehicle bodies or
similar work pieces. A rotary atomizing head to be used on
i5 such a coating machine is largely constituted by an assembly
of a main body and a hub member.
For instance, described in Japanese Laid-Open Patent
Publication No. H9-234393 and its corresponding foreign
patents U.S.P. 5,897,060 and EP0803293A1 is a rotary atomizing
2o head type coating machine employing a rotary atomizing head
body, which is provided with a rotational shaft mount portion
on the rear side for mounting a rotational shaft of an air
motor and which formed in a cylindrical or bell shape in a
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front portion forward of the rotational shaft mount portion.
Further, the rotary atomizing head is provided with a paint
spreading surface on the front portion toward marginal paint
releasing edges for spreading paint into the form of a thin
s film, along with a paint reservoir which is formed on a deeper
portion than the paint spreading surface. Furthermore, a
stepped hub fitting portion is provided between the paint
spreading surface and the paint reservoir of the rotary
atomizing head body.
io On the other hand, the hub member of the rotary atomizing
head is fittingly mounted in position within the hub fitting
portion in such a way as to cover the front side of the paint
reservoir. The hub member is provided with a large number of
paint outlet holes in its outer peripheral portions so that
15 paint in the paint reservoir is allowed to flow out onto the
paint spreading surface through the paint outlet holes.
An 0-ring is fitted either in the inner periphery of the
stepped hub fitting portion or on the outer periphery of the
hub member, and the hub member is removably retained in the
2o stepped hub fitting portion by resilient force of the O-ring.
At the time of washing the rotary atomizing head for a
color change or for other purposes, normally the rotary
atomizing head which is mounted on a coating machine is
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cleaned by the so-called automatic washing operation. Namely,
in the case of an automatic washing operation, the rotary
atomizing head is put in rotation at a high speed, and a wash
fluid such as thinner is supplied from a feed tube to the
s paint reservoir of the rotary atomizing head thereby to wash
away deposited paint from paint contacting portions including
the paint reservoir, front and rear surfaces of the hub
member, paint outlet holes and paint spreading surface.
However, it is usually the case that, after an automatic
1o washing operation, pigment components of the paint still
remain and accumulate in or on the paint contacting portions
although small in amount. Therefore, if the paint residues
solidify in or on the paint contacting portions, the
solidified pigments or other components have to be manually
i5 removed by the use of a brush or the like.
In the case of the rotary atomizing head according to the
above-mentioned Japanese Laid-Open Patent Publication No. H9-
234393, a hub member is removably mounted and retained on a
stepped hub fitting portion by the use of resilient force of
2o an O-ring. In this case, the O-ring has resiliency in such a
degree as to be easily deformable when pushed. Therefore,
when the rotary atomizing head is rotated at a high speed, for
example, at a speed higher than 40,000 rpm, the inside
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diameter of the O-ring is increased by the centrifugal force
which acts on the O-ring.
On the other hand, the rotary atomizing head and the hub
member, which are generally formed of an aluminum alloy,
s stainless alloy or a hard synthetic resin material.
Therefore, even when the rotary atomizing head is put in high
speed rotation, deformations of the rotary atomizing head and
the hub member under the influence of the centrifugal force
are extremely small as compared with the extent of deformation
io of the O-ring .
This means that, when the rotary atomizing head is put in
high speed rotation, the O-ring alone is spread to a larger
diameter under the influence of the centrifugal force, losing
the ability of holding or retaining the hub member securely in
1s position. As a result of the weakened retention force of the
O-ring, there may arise a problem that the hub member starts
rattling within the stepped hub fitting portion.
Besides, repeated mounting and dismantling of the rotary
atomizing head and the hub member can cause deteriorations in
2o resilient force of the O-ring. If the rotary atomizing head
is put in high speed rotation, the O-ring which is in such a
deteriorated state in resilient force is no longer capable of
securely supporting the rotary atomizing head, and the
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rotation of the rotary atomizing head becomes unstable.
Further, as a result of repeated mounting and dismantling of
the rotary atomizing head and the hub member, the O-ring
undergoes abrasive wear due to frictional contact with
associated parts and needs to be replaced at a high frequency.
Moreover, paint which comes out through the paint outlet
holes flows into gap spaces between the stepped hub fitting
portion and outer peripheral portions of the hub member during
a coating operation, and pigment components of the paint tend
1o to accumulate and solidify there even after conducting an
automatic washing operation on the rotary atomizing head even
at time of a color change or for other reasons. Therefore, in
order to remove the solid contaminants like solidified
pigments from the gap spaces, it becomes necessary to
i5 dismantle the hub member from the rotary atomizing head body.
In such a case, it is often found difficult to dismantle the
hub member readily from the main body of the rotary atomizing
head because solidified pigments which has stuck into the gap
spaces act like wedges. If one try to remove the hub member
2o forcibly by applying strong forces to the rear side of the hub
member by the use of a hammer or the like, those portions of
the stepped hub fitting portion of the main body and the hub
member which are in contacting engagement can be damaged to a
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serious degree.
On the other hand, the hub member is provided with a large
number of paint outlet holes. However, for the purpose of
distributing paint from the paint reservoir to the paint
s spreading surface of the rotary atomizing head, a large number
of paint outlet holes of a relatively small diameter are
provided along the outer periphery of the hub member.
Therefore, as paint passes through the paint outlet holes,
pigment components of the paint tend to deposit and accumulate
on inner peripheral surfaces of the paint outlet holes,
gradually constricting the inside diameter of the paint outlet
holes.
As a result of paint deposition and accumulation, the
paint outlet holes are varied in diameter. Therefore, paint
1s which flows out onto the paint spreading surface through the
paint outlet holes becomes unstable in flow rate, making it
difficult to form a thin film of paint uniformly on the paint
spreading surface and releasing from the paint releasing edges
paint particles of such irregular sizes as would invite
2o degradations in coating quality.
In addition, as the paint outlet holes are constricted in
diameter, the paint reservoir is overly filled with paint
which is not allowed to flow out smoothly through the paint
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outlet holes, and the paint begins to overflow into gap spaces
around the rotational shaft to give adverse effects on the
operation of the air motor.
In this regard, according to the prior art, a narrow rod-
s like (a needle-like) tool poked into the paint outlet holes
one after another to remove accumulated and solidified paint
therefrom. This paint removing job is extremely troublesome
and time consuming and invites a serious drop in working
efficiency.
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DISCLOSURE OF THE INVENTION
In view of the foregoing situations, it is an object of
the present invention to provide a rotary atomizing head
employing a main body and a hub member which can be easily
i5 assembled and disassembled.
It is another object of the present invention to provide a
rotary atomizing head which can retain a hub member securely
within a hub fitting groove even when the rotary atomizing
head is put in high speed rotation.
2o It is still another object of the present invention to
provide a rotary atomizing head which permits to remove
solidified pigments or other paint residues from paint
passages in a facilitated manner.
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The present invention is directed to a rotary atomizing
head including a main body formed in a bell or tubular shape
and having on the rear side a rotational shaft mount portion
and on the front side a paint spreading surface extending
s toward marginal paint releasing edges for spreading paint into
the form of a thin film and a paint reservoir provided in a
receded deep portion of the main body, and a hub member fitted
in an inner peripheral surface of the main body in such a way
as to cover up front side of the paint reservoir.
1o According to the present invention, in order to solve the
above-mentioned problems, there is provided a rotary atomizing
head which is characterized in that: the main body is provided
with a hub fitting groove around the inner peripheral surface
between the paint reservoir and the paint spreading surface;
1s the hub member is constituted by a lid portion of a circular
disc-like shape having an outside diameter smaller than inside
diameter of the inner peripheral surface on the side of the
main body, a plural number of leg portions projected axially
rearward from the lid portion and having distal end portions
2o adapted to be brought into and out of engagement with the hub
fitting groove through resilient deformation, and a plural
number of notched grooves each provided between adjacent leg
portions; and a plural number of channel-like paint passages
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are formed by and between the hub fitting groove and the
notched grooves when the leg portions of the hub member are
fitted in the hub fitting groove, and at the same time an
annular paint passage is formed between the inner peripheral
s surface of the main body and circumferential surface of the
lid portion.
With the arrangements just described, by holding the hub
member against the main body in such a way as to cover the
paint reservoir and then pushing it into the main body, the
io leg portions of the hub member, which are formed independently
of each other, are resiliently deformed radially inward of the
inner peripheral surface of the main body and then spread into
a larger diameter upon engagement with the hub fitting groove.
Consequently, the hub member is securely retained and stopped
15 in the hub fitting groove by the resilient force of the leg
portions. When the rotary atomizing head is put in high speed
rotation, the respective leg portions of the hub member are
spread into a larger diameter under the influence of
centrifugal force and strongly pressed against the hub fitting
2o groove to retain the hub member in position with greater
retention forces.
Besides, when the hub member is set in the hub fitting
groove, channel-like paint passages are formed between the
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notched grooves and the hub fitting groove, and at the same
time the annular paint passage is formed between the lid
portion of the hub member and the inner peripheral surface of
the main body. Therefore, at the time of a coating operation,
s paint which has been supplied to the paint reservoir is urged
to flow out onto the paint spreading surface through the
respective channel-like paint passages and annular paint
passage, and sprayed from the paint releasing edges in the
form of finely atomized particles toward a work piece and
1o deposited on the latter.
On the other hand, at the time of removing accumulated and
solidified paint residues including solidified pigments or
other components of paint from the respective channel-like
paint passages and the annular paint passage, the hub member
i5 can be detached from the main body simply by pushing a rear
surface of the hub member through the rotational shaft mount
portion on the front side of the main body. By so doing, the
hub member can be easily disengaged from the hub fitting
groove even when solidified paint residues are stuck in gap
2o spaces between the respective leg portions and the hub fitting
groove, because the leg portions undergo resilient deformation
relatively easily in the same manner as they are pushed into
the hub fitting groove. In a disassembled state, the channel-
CA 02394905 2002-06-07
like paint passages are split into notched grooves on the side
of the hub member and the hub fitting groove on the side of
the main body, so that solidified paint residues like pigments
can be easily removed from the notched grooves and the hub
s fitting groove by the use of a brush or the like. In
addition, accumulated and solidified paint residues can also
be easily removed from other liquid contacting portions
including the inner peripheral surface of the main body and a
paint receiving surface of the hub member.
1o According to the present invention, the leg portions and
the notched grooves are formed alternately at and along outer
periphery of the lid portion, and the channel-like paint
passages are formed independently between the notched grooves
and the hub fitting groove.
1s With the arrangements just described, paint which has been
supplied to the paint reservoir is uniformly distributed to
the annular paint passage through the respective channel-like
paint passages.
According to the present invention, the annular paint
zo passage is formed between and entirely around the inner
peripheral surface of the main body and the circumferential
surface of the lid portion of the hub member.
With the arrangements just described, paint which has been
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passed through the respective channel-like paint passages is
supplied to the paint spreading surface through the annular
paint passage.
According to the present invention, the leg portions are
spread into a larger diameter in a direction away from the lid
portion and toward the distal end portions.
With the arrangements just described, the distal ends of
the respective leg portions, which are located in radially
outermost positions, can be securely brought into fitting
io engagement with the hub fitting groove when the hub member is
pushed into the main body.
According to the present invention, the hub fitting groove
is connected to the inner peripheral surface of the main body
through arcuately rounded surfaces in front and rear boundary
1s regions.
With the arrangements just described, paint is allowed to
flow from the paint reservoir to the paint spreading surface,
smoothly riding over the hub fitting groove without scattering
around at the edges of the hub fitting groove.
2o According to the present invention, the annular paint
passage is gradually diverged into a larger diameter in a
forward direction.
With the arrangements just described, the inner peripheral
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surface of the main body is diverged in diameter from rear to
front side thereof, so that, at the time of mounting the hub
member on the main body, the leg portions of the hub member
can be gradually bent toward the hub fitting groove through
s resilient deformation until they fall into engagement with the
latter. In addition, paint which has been passed through the
respective channel-like paint passages is supplied onto the
paint spreading surface through the annular paint passage.
According to the present invention, the annular paint
1o passage is a straight passage having substantially a uniform
diameter in an axial direction.
With the arrangements just described, paint which has been
passed through the respective channel-like paint passages is
similarly supplied onto the paint spreading surface through
i5 the annular paint passage.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. 1 is a schematic sectional view of a rotary atomizing
2o head type coating machine with a rotary atomizing head
embodying the present embodiment;
Fig. 2 is an enlarged sectional view of the rotary
atomizing head shown in Fig. 1;
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Fig. 3 is an enlarged sectional view of major component
parts, taken in the direction of arrows III-III in Fig. 2;
Fig. 4 is an enlarged sectional view of major component
parts, taken in the direction of arrows IV-IV in Fig. 2;
s Fig. 5 is an exploded sectional view of a main body of the
rotary atomizing head and a hub member;
Fig. 6 is an enlarged sectional view, showing a hub
fitting groove and associated parts on an enlarged scale;
Fig. 7 is a schematic front view, showing the hub member
1o alone on an enlarged scale;
Fig. 8 is a right-hand side view of the hub member, taken
in the direction of arrows VIII-VIII of Fig. 7; and
Fig. 9 is an enlarged sectional view similar to Fig. 2,
but showing a modification of the rotary atomizing head
is according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereafter, a rotary atomizing head type coating machine
employing a rotary atomizing head according to the present
2o invention is described more particularly by way of its
preferred embodiment with reference to Figs. 1 through 8.
In the drawings, indicated at 1 is a cover of a rotary
atomizing head type coating machine, which is formed in a
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cylindrical shape to accommodate therein an air motor 2 as
described below.
Denoted at 2 is the air motor which is housed in the cover
1. The air motor 2 is largely constituted by a tubular motor
casing 2A, an air turbine 2B which is accommodated in the
motor casing 2A, and a static air bearing 2C for rotatably
supporting a rotational shaft 3, which will be described
hereinafter. The air motor 2 drives the rotational shaft 3 by
compressed air which is supplied to the air turbine 2B.
1o Indicated at 3 is a hollow rotational shaft which is
rotatably supported by the static air bearing 2C of the air
motor 2. The fore end of the rotational shaft 3 is projected
on the front side of the air motor 2, a rotary atomizing head
11 is mounted on a projected fore end portion of the
rotational shaft 3 as described more particularly hereinafter.
The base end of the rotational shaft 3 is connected to the air
turbine 2B.
Indicated at 4 is a feed tube which is passed through the
hollow rotational shaft 3. The fore end of the feed tube 4 is
2o projected forward of the rotational shaft 3 and extended into
the rotary atomizing head 11. The feed tube 4 is of a coaxial
double tube construction providing a paint passage 4A which is
located centrally on the inner side to serve as a conduit for
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paint or a wash fluid like thinner, and an outer annular
thinner passage 4B which is located on the outer side to serve
as a conduit for thinner. At the time of a coating operation,
paint is supplied through the paint passage 4A of the feed
tube 4 toward the rotary atomizing head 11. On the other
hand, at the time of a washing operation for a color change,
for example, thinner is supplied through the paint passage 4A
for washing front surfaces of the hub member 14, which will be
described after, and at the same time thinner is supplied
1o through the thinner passage 4B for washing the paint spreading
surface 12C and paint releasing edges 12D of a main body 12.
Designated at 5 is a shaping air ring which is attached to
the fore end of the cover 1. The shaping air ring 5 is
generally formed in an annular shape and provided with a large
number of air outlet holes 5A on its front side. The air
outlet holes 5A are located on the front side of the shaping
air ring 5 to spurt air for controlling a spray pattern of
paint particles which are sprayed by the rotary atomizing head
11.
2o Now, indicated at 11 is a rotary atomizing head according
to an embodiment of the present invention, which is mounted on
a fore end portion of the rotational shaft 3. As shown in
Fig. 2, the rotary atomizing head 11 is largely constituted by
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a main body 12, a hub fitting groove 13, a hub member 14,
channel-like paint passages 19, and an annular paint passage
20.
Indicated at 12 is a main body of the rotary atomizing
head 11, which defines the outer configuration of the rotary
atomizing head 11 and which is diverged in a bell shape in a
forward direction from its rear side. The main body 12 is
formed, for example, of aluminum alloy, stainless alloy, hard
synthetic resin material or the like. In this regard, in the
1o case of a synthetic resin material, the main body 12 is
entirely formed of a conductive synthetic resin material, or a
conductive synthetic resin material is coated on a main body
12 of a non-conductive synthetic resin material. Accordingly,
a high voltage can be applied to the main body 12 during a
is coating operation, and paint which flows on or along surfaces
of the main body 12 can be directly charged with a high
voltage.
On the rear side, the main body 12 of the rotary atomizing
head is formed into a tubular rotational shaft mount portion
20 12A, which is provided with an internal or female screw
portion 12A1 in a deep inner portion for threaded engagement
with the rotational shaft 3 of the air motor 2. Further, the
main body 12 is formed with an annular partition wall 12B
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which is projected radially inward in such a way as to block
deep end portions of the rotational shaft mount portion 12A.
A fore end portion of the feed tube 4, which is projected from
the fore distal end of the rotational shaft 3, is inserted in
s the inner periphery of the annular partition wall 12B.
On the other hand, on the front side, the main body 12 is
provided with a forwardly diverging paint spreading surface
12C of a saucer-like shape, which is expanded continuously
toward and as far as paint releasing edges 12D at the front
1o end (at the outer end) of the main body 12 for spreading paint
into a thin film. Further, the main body 12 is provided with
a paint reservoir 12E in a deep portion between the annular
partition wall 12B and the hub member 14, which will be
described hereinafter. The paint reservoir 12E serves as a
1s space for temporarily holding and spreading paint which is fed
through the feed tube 4. Further, as shown in Fig. 5, an
inner peripheral surface 12F between the paint reservoir 12E
and the paint spreading surface 12C of the main body 12 is
gradually increased in diameter in the forward direction to
2o provide a forwardly diverging surface. Furthermore, at the
front end (bounding on the paint spreading surface 12C), the
forwardly diverging inner peripheral surface 12F is formed to
have an inside diameter D1 larger than a maximum inside
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diameter D2 of a hub fitting groove 13 which will be described
hereinafter (D1 > D2).
As paint is supplied to the paint reservoir 12E on the
main body 12 of the rotary atomizing head which is put in high
s speed rotation, the paint is fed onto the paint spreading
surface 12C through channel-like paint passages 19 which will
be described hereinafter. Then, the paint which has been
supplied onto the paint spreading surface 12C is spread into
the shape of a thin film and sprayed forward from the paint
io releasing edges 12D in the form of finely atomized particles.
Indicated at 13 is a hub fitting groove which is provided
on an inner peripheral surface 12F of the main body 12. The
hub fitting groove 13 is disengageably engaged with fore end
portions of leg portions 17 of the hub member 14, which will
is be described after. The hub fitting groove 13 is formed
around the forwardly diverging inner peripheral surface 12F at
an intermediate portion between front and rear ends of the
latter, and in an arcuate shape in cross section. Further, as
shown in Fig. 6, the hub fitting groove 13 is adjoined with
2o the inner peripheral surface 12F through arcuately rounded
surfaces 13A and 13B on the front and rear sides,
respectively. These rounded surfaces 13A and 13B function to
let paint flow across the hub fitting groove 13 smoothly
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without scattering as paint is supplied toward the paint
spreading surface 12C from the paint reservoir 12E.
In this instance, the hub fitting groove 13 is arranged to
have a maximum inside diameter D2 which is larger than inside
s diameter D3 of the front rounded surface 13A but smaller than
inside diameter D1 at the front end of the forwardly diverging
inner peripheral surface 12F (D1>D2>D3). Further, in this
instance, arrangements are made such that the maximum inside
diameter D2 of the hub fitting groove 13 is same as or
1o slightly smaller than maximum outside diameter D6 of the leg
portions 17 of the hub member 14, which will be described
hereinafter (D2~ D6). With these arrangements, the leg
portions 17 of the hub member 14 can be tightly snapped into
the hub fitting groove 13, riding over the front arcuately
is rounded surface 13A, and the hub member can be retained
securely in the hub fitting groove 13 free of rattling
movements.
Indicated at 14 is the hub member which is detachably
mounted on the main body 12 of the rotary atomizing head in
2o such a way as to cover up the front side of the paint
reservoir 12E. The hub member 14 is formed substantially in a
circular shape by the use of a material which is easily
deformable under the influence of centrifugal force, namely, a
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synthetic resin material with suitable resiliency and
flexibility such as polyether sulfon (PES), polyphenylene
sulfide (PPS), polyether imide (PEI), polyether ether ketone
(PEEK), polyoxymethylene (POM), polyamide imide (PAI),
s polyethyleneterephthalate (PET), polyimide (PI) and the like.
As shown in Fig. 7, the hub member 14 is largely constituted
by a lid portion 15, leg portions 17 and notched grooves 18.
The reference numeral 15 indicates a lid portion of a
circular shape which constitutes a main body of the hub member
14. The lid portion 15 is located in such a way as to close
the front side of the above-described paint reservoir 12E, and
provided with a flat front surface 15A and a paint receiving
surface 15B on its front and rear sides, respectively. Paint
which is fed through and discharged from the feed tube 4 is
is received by the paint receiving surface 15B. In this case,
the lid portion 15 has a circumferential surface 15C of an
outside diameter which is gradually increased from its rear to
front end, namely, having an outside diameter D4 at its front
end which is larger than an outside diameter D5 at its rear
2o end (D4>D5). The outside diameter D4 at the front end of the
lid portion 15 is set at a value which is smaller than the
inside diameter D1 at the front end of the forwardly diverging
inner peripheral surface 12F of the main body 12 (D1>D4).
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Further, the outside diameter D5 at the rear end of the lid
portion 15 is set at a value which is smaller than the inside
diameter D3 at the arcuately rounded surface 13A on the front
side of the hub fitting groove 13 (i.e., at the rear end of
the forwardly diverging inner peripheral surface 12F) (D3>D5).
On the other hand, a conical projection 15D which is
projected in a rearward direction is formed at the center of
the paint receiving surface 15B, thereby to smoothly handle
paint which is discharged from the feed tube 4. In this
io instance, when the hub member 14 is mounted on the main body
12 of the rotary atomizing head, the circumferential surface
15C of the lid portion 15 is inwardly spaced from the inner
peripheral surface 12F of the main body 12 by a gap of a
predetermined width to provide an annular paint passage 20
which will be described hereinafter.
Denoted at 16 are four thinner outlet holes which are
provided across and in center portions of the lid portion 15.
More specifically, these thinner outlet holes 16 are bored
through the paint receiving surface 15B (outer skirt portions
of the conical projection 15D) and the front surface 15A of
the lid portion 15. The thinner outlet holes 16 serve as
passages for supplying thinner to the front surface 15A from
the side of the paint receiving surface 15B at the time of
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washing deposited paint off the front surface 15A.
Indicated at 17 are a plural number of leg portions
(fourteen leg portions in the case of the particular
embodiment shown) which are formed integrally with and at
s intervals along the outer periphery of the lid portion 15 on
the rear end thereof. Namely, as shown in Fig. 8, these leg
portions 17 are formed independently of each other and at
uniform intervals at and along the outer periphery on the rear
side of the lid portion 15. Further, the leg portions 17 are
io each extended in a radially outward direction from an outer
peripheral edge portion on the rear side of the lid portion 15
and are gradually spread into a larger diameter as they are
extended away from the outer periphery of the lid portion 15
toward outer distal ends 17A (in an axially rearward
15 direction). Maximum outside diameter D6 at the outer distal
ends 17A of the leg portions 17 is larger than the outside
diameter D5 of the rear end of the lid portion 15 (D6>D5).
Each one of the outer distal ends 17A of the leg portions 17
is a free end which is formed in a spherical shape
2o substantially conforming with the profile of the hub fitting
groove 13.
Moreover, the maximum outside diameter D6 at the outer
distal ends 17A of the leg portions 17 is set at a value which
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is same as or smaller than the outside diameter D4 at the
front end of the lid portion 15 (D6~ D4). Furthermore, the
maximum outside diameter D6 (at the outer distal ends 17A) of
the leg portions 17 is set at a value which is same as or
slightly larger than the maximum inside diameter D2 of the hub
fitting groove 13 (D6? D2).
The leg portions 17, which are formed independently of
each other, are resiliently deformable in a relatively easy
manner and therefore can be easily fitted in or detached from
1o the hub fitting groove 13. Besides, since the maximum outside
diameter D6 at the outer distal ends of the leg portions 17 is
same as or slightly larger than the maximum inside diameter D2
of the hub fitting groove 13, the respective leg portions 17
can be securely retained in the hub fitting groove 13.
i5 As described above, the inside diameter D1 at the front
end of the inner peripheral surface 12F, maximum inside
diameter D2 of the hub fitting groove 13, and inside diameter
D3 at the arcuately rounded surface 13A on the front side of
the hub fitting groove 13 on the main body 12, outside
2o diameter D4 at the front end of the lid portion 15 of the hub
member 14, outside diameter D5 at the rear end of the lid
portion 15, and maximum outside diameter D6 at the outer
distal ends 17A of the leg portions 17 of the hub member 14
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are in the following dimensional relations (1).
D1>D2>D3,
D4 ~ D6 >D5 ,
D6? D2, ..............(1)
D1>D4, and
D3>D5
Indicated at 18 are a plural number of notched grooves
(fourteen notched grooves in the case of the particular
embodiment shown) which are formed alternately with the leg
1o portions 17 in outer peripheral portions on the back side of
the lid portion 15. These notched grooves 18 are each formed
in U-shape between adjacent leg portions 17 and are located at
uniform intervals along the outer periphery of the lid
portion. When the leg portions 17 of the hub member 14 are
fitted in the hub fitting groove 13, the notched grooves 18
form channel-like paint passages 19 between the hub fitting
groove 13.
Indicated at 19 are a plural number of channel-like paint
passages which are formed between an inner peripheral surface
of the hub fitting groove 13 and the respective notched
grooves 18 when the hub member 14 is mounted and set in
position on the main body 12. As shown in Fig. 3, the
channel-like paint passages 19 are provided at uniform
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CA 02394905 2002-06-07
intervals in the circumferential direction, alternately with
the leg portions 17 and in a large number which corresponds to
the number of the notched grooves 18. As the rotary atomizing
head 11 is put in high speed rotation and paint is supplied to
s the paint reservoir 12E from the feed tube 4, the channel-like
paint passages 19 function to distribute paint uniformly
toward an annular paint passage 20, which will be described
hereinafter .
Indicated at 20 is an annular paint passage which is
io formed between the forwardly diverging inner peripheral
surface 12F of the main body 12 and circumferential surface
15C of the lid portion 15 when the hub member 14 is mounted on
and set in position on the main body 12. As shown in Figs. 2
and 4, the annular paint passage 20 is formed in a ring-like
15 annular shape around between the circumferential surface 15C
of the hub member 14 and the inner peripheral surface 12F of
the main body 12, and is gradually increased in diameter in
the forward direction. Accordingly, the forwardly spreading
annular paint passage 20 is capable of distributing paint
2o uniformly between the forwardly diverging inner peripheral
surface 12F of the main body 12 and the circumferential
surface 15C of the lid portion 15, and circulating thinner
therethrough in contact with the above-mentioned surfaces 15C
26
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CA 02394905 2002-06-07
and 12F.
In this instance, the width a at the front end of the
annular paint passage 20 (shown in Fig. 2) is in the following
dimensional relations (2).
s a '--. (D1 - D4)/2 .. .. . . ... ... . . (2)
The rotary atomizing head 11, with the construction
according to the present embodiment of the invention, is
operated or handled in the manner as described below, in an
assembling work, in a coating operation by the rotary
1o atomizing head 11 and in removing (dissolving) solidified
pigment component of paint after a coating operation.
For assembling the rotary atomizing head 11, the hub
member 14 is mounted and set in position on the main body 12
in the manner as described below.
1s In the first place, one holds the hub member 14 in such a
way as to cover the front side of the paint reservoir 12E, and
pushes in the hub member 14 toward the paint reservoir 12E.
At this time, since the inside diameter D1 at the front end of
the forwardly diverging inner peripheral surface 12F of the
2o main body 12 is larger than the maximum outside diameter D6 of
the leg portions 17, the hub member 14 can be positioned at
the center of the main body 12. Besides, along the inner
peripheral surface 12F which is gradually reduced in diameter
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CA 02394905 2002-06-07
in an inward or rearward direction, the leg portions 17 of the
hub member 14 can be gradually bent in a radially inward
direction through resilient deformation until they ride over
the front arcuately rounded surface 13A on the front side of
the hub fitting groove 13. Therefore, the leg portions 17 of
the hub member 14 can be easily urged into fitting engagement
with the hub fitting groove 13. Further, since the leg
portions 17 are formed independently of each other, they can
be flexed relatively easily and therefore can be urged into
to engagement with the hub fitting groove 13 quite easily.
In addition, the maximum outside diameter D6 of the leg
portions 17 of the hub member 14, which are in engagement with
the hub fitting groove 13, is same as or slightly larger than
the maximum inside diameter D2 of the hub fitting groove 13,
1s so that the respective leg portions 17 can be tightly and
securely retained in the hub fitting groove 13.
Now, after assembling as described above, the rotary
atomizing head 11 is used in a coating operation for spraying
paint toward a work piece in the manner as follows.
2o Firstly, the rotary atomizing head il is rotationally
driven from the air motor 2 through the rotational shaft 3 and
put in high speed rotation, for example, at a speed of 3,000
to 100,000 rpm. At this time, centrifugal force acts on the
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CA 02394905 2002-06-07
main body 12 and the hub member 14 of the rotary atomizing
head 11. However, the respective leg portions 17 of the hub
member 14, which are formed independently of each other, are
easily resiliently deformable and tend to spread in a radial
direction to a greater degree than the main body 12.
Therefore, the respective leg portions 17 are strongly pressed
against the hub fitting groove 13 to retain the hub member 14
within the hub fitting groove 13 in a tight and secure manner
all the more.
to Upon supplying paint from the feed tube 4 toward the paint
receiving surface 15B of the hub member 14, the paint which
has been delivered to the paint receiving surface 15B is urged
to flow from the paint reservoir 12E and then flow out onto
the paint spreading surface 12C of the main body 12 through
i5 the respective channel-like paint passages 19 and the annular
paint passage 20 under the influence of centrifugal force. At
this time, since the channel-like paint passages 19 are formed
at uniform intervals around the entire circumference of the
lid portion 15, the paint which has been supplied to the paint
2o reservoir 12E is uniformly distributed onto the paint
spreading surface 12C on the main body 12 through the channel-
like paint passages 19. In addition, since the annular paint
passage 20 is formed in a predetermined width a, paint can be
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CA 02394905 2002-06-07
urged to flow out uniformly around the entire circumference of
the lid portion. Paint is spread into a thin film on the
paint spreading surface 12C and sprayed from the paint
releasing edges 12D in the form of finely atomized particles
toward a work piece to be coated.
During a coating operation, paint flowing on the surfaces
of the main body 12 can be directly charged with a high
voltage, by applying a high voltage to the rotary atomizing
head 11 from a high voltage generator which is not shown.
1o Charged paint particles are put on a flight toward a work
piece and can be deposited on the latter at a higher
deposition rate.
Now, upon finishing a coating operation in one color, the
paint color can be changed in the manner as follows.
Firstly, prior to changing the paint color, a previous
color which has deposited on various parts of the rotary
atomizing head is washed off by the so-called automatic
washing operation. In an automatic washing operation, while
the rotary atomizing head 11 is put in high speed rotation,
2o thinner is supplied to the paint passage 4A of the feed tube 4
and then from the paint passage 4B toward the rotary atomizing
head 11. At this time, since the annular paint passage 20
with a predetermined width a is gradually diverged in diameter
CA 02394905 2002-06-07
in the forward direction, thinner is also supplied to the
circumferential surface 15C of the hub member 14.
Accordingly, deposited previous color on the forwardly
diverging inner peripheral surface 12F and the circumferential
surface 15C of the hub member can be efficiently washed off by
the thinner which flows through the annular paint passage 20.
In addition, deposited paint on the paint spreading surface
12C and paint releasing edges 12D of the main body 12 is
washed off by thinner which flows out through the channel-like
1o paint passages 19, while the front surface 15A of the hub
member 14 is washed by thinner which flows out through the
thinner outlet holes 16.
On the other hand, paint residues in gap spaces in or
between the notched grooves 18, hub fitting groove 13 and the
i5 respective leg portions 17 of the hub member 14 are difficult
to remove by the above-described automatic washing operation.
Therefore, pigment components of deposited paint tend to
accumulate and solidify little by little within the notched
grooves 18 of the hub member 14 or similar parts. In order to
2o remove solidified paint residues of this sort, the rotary
atomizing head 11 is disassembled, for removing the solidified
paint residues from the hub member 14 in a disassembled state.
On such an occasion, for example, a rotary atomizing head is
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CA 02394905 2002-06-07
disassembled and solidified paint residues are removed in the
manner as described below.
In the first place, the rotary atomizing head 11 is
dismantled from the rotational shaft 3 prior to removing the
s hub member 14 from the main body 12. In the next place, a
rod-like disassembling jig (not shown) is inserted into the
rotational shaft mount portion 12A of the main body 12,
pushing the hub member 14 with the dig from behind. By so
doing, the hub member 14 can be easily dismantled from the hub
1o fitting groove 13 through resilient deformation of the leg
portions 17 which are formed independently of each other and
easily resiliently deformable, for example, even in a case
where solidified paint residues are stuck in gap spaces
between the leg portions 17 and the hub fitting groove 13.
15 Upon removing the hub member 14 from the main body 12 in
this manner, the respective channel-like paint passages 19 are
divided into the hub fitting groove 13 on the side of the main
body 12 and the notched grooves 18 on the side of the hub
member 14. In this state, solidified paint residues can be
2o easily removed simply by scraping the hub fitting groove 13
and the notched grooves 18 with a brush or the like.
Solidified paint residues on other paint contacting parts, for
example, on or in the paint reservoir 12E and inner peripheral
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CA 02394905 2002-06-07
surface 12F of the main body 12 and the circumferential
surface 15C and leg portions 17 of the hub member 14, which
are difficult to wash, can also be easily removed in a manner
similar to the hub fitting groove 13 and the notched grooves
1$.
Thus, according to the present embodiment of the
invention, the main body 12 of the rotary atomizing head is
formed of a metallic material or a hard synthetic resin
material, while the hub member 14 is formed of a synthetic
1o resin material with a suitable degree of resiliency and
flexibility. In addition, the hub fitting groove 13 is
provided on and around the forwardly diverging inner
peripheral surface 12F, and the hub member 14 is provided with
leg portions 17 to be disengageably engaged with the hub
fitting groove 13. Accordingly, at the time of mounting the
hub member 14 on the main body 12, the hub member 14 is held
against the inner peripheral surface 12F of the main body 12
and then pushed in, whereupon the leg portions 17 of the hub
member are forcibly urged into engagement of the hub fitting
2o groove 13 through resilient deformation.
As a consequence, when the rotary atomizing head 11 is put
in high speed rotation, the leg portions 17 of the hub member
14, which is formed of a synthetic resin material with a
33
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CA 02394905 2002-06-07
suitable degree of resiliency and flexibility, are strongly
pressed against the bottom of the hub fitting groove 13 and
therefore imparted with an enhanced retention force in holding
the hub member 14 in position on the main body 12, precluding
possibilities of falling accidents of the hub member 14 to
ensure improved reliability of the rotary atomizing head 11.
Besides, the rotational balance of the hub member 14 can be
maintained in a stable state over a prolonged period of time.
On the other hand, at the time of removing accumulated and
1o solidified pigments or other paint components from the notched
grooves 18 and gap spaces between the hub fitting groove 13
and the respective leg portions 17 which are normally
difficult to clean by an automatic washing operation, the hub
member 14 can be easily detached from the main body 12 by
pushing the hub member 14 from the side of the rotational
shaft mount portion 12A of the main body 12 by the use of a
disassembling jig. In the disassembled state, the channel-
like paint passages 19 can be divided into the hub fitting
groove 13 on the side of the main body 12 and the notched
2o grooves 18 on the side of the hub member 14. Therefore,
solidified paint residues in or on the hub fitting groove 13
and notched grooves 18 can be easily scrubbed off by the use
of a brush or the like. This improves the efficiency of the
34
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CA 02394905 2002-06-07
cleaning job to a significant degree.
Further, the annular paint passage 20 is formed
substantially in a uniform width _a, so that paint can be
distributed uniformly around the entire circumference during a
coating operation, making it possible to improve the quality
of coatings. On the other hand, at the time of a washing
operation, deposited paint on the inner peripheral surface 12F
of the main body 12 and the circumferential surface 15C of the
hub member 14 can be washed off efficiently by thinner,
1o permitting to finish the washing operation in an efficient
manner.
Furthermore, since the leg portions 17 of the hub member
14 are formed independently of each other, they are
resiliently deformable quite easily when bringing them into
is and out of engagement with the hub fitting groove 13.
Accordingly, for example, even in a case where solidified
pigments or other components of paint is stuck in the channel-
like paint passages 19 between the leg portions 17 and the hub
fitting groove 13 as mentioned hereinbefore in connection with
2o the prior art, the hub member 14 can be put on or off easily
by pressing or pulling with finger tips, facilitating the
mounting and dismantling jobs to a considerable degree.
Moreover, the hub fitting groove 13 is connected to the
CA 02394905 2002-06-07
forwardly diverging inner peripheral surface 12F through
arcuately rounded surfaces 13A and 13B at the front and rear
boundary regions. Therefore, paint is allowed toward the
paint spreading surface 12C from the paint reservoir 12E,
s smoothly riding over the hub fitting groove 13 without
scattering around at the boundary regions. Thus, the
arcuately rounded surfaces 13A and 13B function to ensure
smooth paint flow across the main body 12 and to improve the
quality of coatings.
to Further, by the provision of the annular paint passage 20
which is diverged or increased in diameter in the forward
direction, the inner peripheral surface 12F of the main body
12 is also diverged in the forward direction from its rear
end. Therefore, at the time of mounting the hub member 14 on
15 the main body 12, the hub member 14 can be readily located at
the center of the main body 12 and easily mounted in position
on the latter in an accurate manner.
On the other hand, as described hereinbefore, the leg
portions 17 of the hub member 14 are formed independently of
2o each other and are relatively easily susceptible to resilient
deformation, so that, even in a case where the hub member 14
is formed of a metallic material or a hard synthetic resin
material similarly to the main body 12, each one of the leg
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CA 02394905 2002-06-07
portions 17 can be easily flexed and imparted with a
sufficient retention force within the hub fitting groove 13.
In the foregoing preferred embodiment, the present
invention has been described by way of a rotary atomizing head
having the forwardly diverging inner peripheral surface 12F
which is gradually increased in diameter in the forward
direction between the main body 12 and the hub member 14 of
the rotary atomizing head, along with the annular paint
passage 20 which is also increased in diameter in the forward
1o direction and formed between and along the inner peripheral
surface 12F and the circumferential surface 15C of the lid
portion 15.
However, the present invention is not limited to a rotary
atomizing head as shown in the foregoing embodiment. For
i5 instance, the invention can be similarly applied to a rotary
atomizing head 31 which is shown as a modification in Fig. 9.
In this case, the rotary atomizing head 31 is largely
constituted by a main body 32 having a rotational shaft mount
portion 32A, an annular partition wall 32B, a paint spreading
2o surface 32C, paint releasing edges 32D, a paint reservoir 32E,
an inner peripheral surface 32F and a hub fitting groove 33
provided on the inner peripheral surface 32F, a hub member 34
having a lid portion 35, thinner outlet holes 36, leg portions
37
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CA 02394905 2002-06-07
37 and notched grooves 38, and channel-like paint passages 39
which is formed between the hub fitting groove 33 and the
notched grooves 38. An annular paint passage 40 with a
uniform diameter from rear to front side is formed between the
straight inner peripheral surface 32F having a substantially
uniform diameter and a circumferential surface 35C of the lid
portion 35.
Accordingly, in the case of this modification, paint which
has passed through the channel-like paint passages 39 can be
1o supplied to the paint spreading surface 32C by the straight
annular paint passage 40 of uniform diameter. When a wash
fluid like thinner is supplied, deposited paint residues in
the annular paint passage 40 can be washed away with the wash
f luid .
i5 Further, in the particular embodiment shown, the hub
member 14 is provided with fourteen leg portions 17. However,
needless to say, the present invention is not limited to this
particular arrangement. The number of leg portions 17 is not
important as long as it is sufficient for retaining the hub
2o member 14 securely on the main body 12 of the rotary atomizing
head, namely, in some cases if suffices if the hub member 14
is provided with at least three leg portions at intervals in
the circumferential direction. In a case where the hub member
38
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' CA 02394905 2002-06-07
is provided with a reduced number of leg portions 17, the
channel-like paint passages are elongated in the
circumferential direction into the shape of a long slot or the
like.
s On the other hand, in the particular embodiment shown, the
main body 12 of the rotary atomizing head 11 is formed of a
metallic material or a conductive synthetic resin material to
serve for a directly charging rotary atomizing head type
coating machine in which paint is directly charged with a high
1o voltage applied through the main body 12 or the like.
However, the present invention is not limited to the directly
charging type. For instance, the present invention is
similarly applicable to an indirectly charging rotary
atomizing head type coating machine which is provided with an
15 external electrode on the outer side of the cover 1 for the
purpose of indirectly charging sprayed paint particles.
Further, in the particular embodiment shown, the main body
12 of the rotary atomizing head is formed in a bell shape.
However, the main body may be formed in a tubular shape which
2o is gradually increased in diameter in the forward direction
from the rotational shaft mount portion toward the paint
releasing edges.
39
